With the rapid progress of nano scientific technology, demands on nano-scaled materials are greatly increasing and the size of an electronic device is more and more decreasing. Thus, studies have been continuously conducted to develop next-generation electronic devices such as a semiconductor device having an ultra micropattern by photolithography, electron beam lithography or EUV (extreme ultraviolet) lithography, dip-pen lithography, nanoimprint lithography, block copolymer lithography, etc.
Among them, block copolymer lithography overcomes the technical limitation of the existing photolithography, for example, a limitation in the pattern size to be formed, and also forms a nanostructure or a nanopattern in an easier and inexpensive manner by self-assembly of block copolymers. Further, the material structure of the block copolymer can be made of a polymer material similar to the photoresist currently used, and thus it can be more easily applied to a current semiconductor manufacturing process.
Further, the block copolymer includes polymer blocks having different chemical structures, connected through a covalent bond, and according to the compositions of the blocks constituting the block copolymer, the length of the chain, and Flory-Huggins parameter, it may form various nanostructures including a complicated three-dimensional structure such as a gyroid or a HPL (hexagonal perforated lamellae) structure, as well as a basic structure such as a sphere, a cylinder, or a lamellae. Also, the nanostructure may be controlled to have various sizes, according to chemical structure of the block copolymer, the compositional ratio of blocks, the molecular weight thereof, etc. The block copolymer lithography has attracted much attention due to applicability of a non-destructive process, simple production of a template for high density arrangement of nano-scale patterns, etc. In particular, among the micro-phases of block copolymer, a block copolymer having a cylindrical structure has a variety of applications including a flash memory, a storage medium, an optical device, an electronic circuit, etc., and thus it is most commonly applied to a block copolymer film or lithography using the same. For such application, it is very important to easily control the orientation and arrangement of the cylindrical nanostructure in a desired shape.
Meanwhile, a silicon oxide nanodot or a metal nanodot has received much attention as a nanopattern type of a material applicable to the fields such as an optical device, an optical waveguide, a chemical sensor, a magnetic storage medium, etc. Therefore, recent studies have been actively conducted to form the nanodot-shaped nanopattern using the cylindrical nanostructure of the block copolymer.
For example, it was suggested that silicon oxide is selectively reacted with a hydrophilic PEO block using a sol-gel precursor (block copolymer) such as poly(styrene-b-ethylene oxide) (PS-b-PEO), and then calcination is performed to remove all of the block copolymers, thereby forming a silicon oxide nanostructure. In the similar way, it was also suggested that a poly(styrene-b-methyl methacrylate) (PS-b-PMMA) thin film oriented perpendicular to a substrate is formed as a template, and PMMA is removed after degraded by UV radiation, and then tetraethoxysilane is introduced into the PMMA-removed pore or tetraethoxysilane is selectively treated to the PMMA block without UV radiation, thereby forming a silicon oxide nanostructure. Additionally, it was also suggested that a thin film such as poly(styrene-b-dimethylsiloxane) (PS-b-PDMS), poly(styrene-b-4-vinyl pyridine) (PS-b-P4VP), etc. is formed and then treated with UV/ozone, or the pores in the thin film are filled with PDMS, etc., and then treated with oxygen plasma, thereby forming a silicon oxide nanodot.
However, the previous experimental results showed a disadvantage in that the nanodot formation process becomes complicated, because use of a sol-gel precursor or an additional PDMS coating process is needed after selectively removing small blocks or segments constituting the cylindrical structure of the block copolymer, in order to form a silicon oxide nanodot. Further, it is difficult to form high aspect ratio nanodots in most block copolymers. When metal nanodots are formed according to the previous experimental results, a complicated subsequent process is also required after formation of nanohole-type patterns. However, a block copolymer or a related technology which can be used for more easily forming nanopatterns such as silicon oxide nanodots, metal nanodots, etc. in a desired shape has not been developed yet.